Currently, GPS is more and more widely applied in mobile terminals (also known as terminals or user terminals, such as mobile phones), and the mobile terminals have higher and higher requirements on the GPS performance. The calibration of GPS in the mobile terminals plays a very important role in improving the GPS performance. The GPS calibration methods in the related art will be described below.
In the related art, there are the following GPS calibration methods: 1. Take a small number of terminal samples to calibrate, acquire a mean value, and then write the parameter into all terminals. 2 Calibrate each terminal independently and write the respective calibration values to the respective terminals. 3. Provide an approximate Doppler frequency shift of the GPS signal through an A-GPS server, the A-GPS server has a reference GPS receiver that can calculate out the Doppler frequency shift of the satellite signal. 4. Optimize and implement with a positioning software estimation algorithm, and in the frequency shift estimation theory, most frequency estimation problems can be attributed to the problem of maximum likelihood estimation, but in many real-time applications that require rapid estimation and correction of the frequency shift, a calculation that takes a lot of time is undesirable. 5 According to the position and velocity of the satellite relative to the ground station, pre-calculate the Doppler frequency shift of the signal, based on which, correct the local oscillation frequency output by the digital frequency synthesizer in the receiver in real time, so as to achieve the purpose of eliminating the Doppler frequency shift.
All the above-mentioned methods have some disadvantages, for example, the calibration values in the method 1 are too simple and can not meet the requirements on the diversity of GPS parameters; the process of the method 2 is complicated, and the calibration process takes a a long time, which is not conducive to large-scale production in batches; and the method 3 requires the assistance of the A-GPS, which consumes terminal traffic and network resources; the software algorithm in the method 4 is complicated and is an approximation algorithm, thus its actual accuracy is not high; the method 5 needs the aid of large-scale test and pre-inference algorithm, thus it has little significance in actual application of the terminal.